The countess was presented to Catherine of Braganza, the wife of Charles II of England upon her arrival in London and was appointed as lady-in-waiting to the queen at Hampton Court Palace. She attended the queen at Greenwich Palace when the latter met her mother-in-law, Queen Henrietta Maria, for the first time (August 1662). During the outbreak of the plague (1665) the countess accompanied the queen and her household to the safety of Hampton Court, later removing to Oxford. She accompanied the king and queen to Dover to farewell the Duchesse d'Orleans on her final visit (June 1670). During the plots directed against the queen and other prominent Catholic figures, the countess and others of the queen's ladies came under the suspicion of being secret papists (1678).

Lady Ossory served Queen Catherine for over twenty years, retiring from service after the death of Charles II (1685). A famous beauty, her portrait was painted by Wissing. She was buried in Westminster Abbey in London on 12 December 1688.